update t
set id=tt.id
from YOUR_TABLE t
join (
    select row_number() over(partition by FIELD1 order by FIELD2) id, FIELD1, FIELD 
    from YOUR_TABLE
    ) tt on t.FIELD1=tt.FIELD1 and t.FIELD2=tt.FIELD2

update t
set id=tt.id
from YOUR_TABLE t
join (
    select row_number() over(partition by FIELD1 order by FIELD2) id, FIELD1, FIELD 
    from YOUR_TABLE
    ) tt on t.FIELD1=tt.FIELD1 and t.FIELD2=tt.FIELD2

WITH CTE(id,n) AS (SELECT id,ROW_NUMBER()OVER(ORDER BY(SELECT 0)))
UPDATE CTE SET id=n;

WITH CTE(id,n) AS (SELECT id,ROW_NUMBER()OVER(ORDER BY(SELECT 0)))
UPDATE CTE SET id=n;

WITH CTE(id,n) AS (SELECT id,ROW_NUMBER()OVER(ORDER BY(SELECT 0))FROM [Таблица])
UPDATE CTE SET id=n;

DECLARE @id int
SET @id = 0
Update YOUR_TABLE
Set ID_FIELD=@id,
      @id=@id+1

ALTER TABLE <table name> ALTER COLUMN <column name> int identity (1,1) NOT NULL

DECLARE @id int
SET @id = 0
Update YOUR_TABLE
Set ID_FIELD=@id,
      @id=@id+1

ALTER TABLE <table name> ALTER COLUMN <column name> int identity (1,1) NOT NULL

ALTER TABLE <table name> ALTER COLUMN <column name> int identity (1,1) NOT NULL
GO
ALTER TABLE <table name> ALTER COLUMN <column name> int NOT NULL
GO

ALTER TABLE <table name> ADD ID int identity (1,1) NOT NULL
GO
ALTER TABLE <table name> ALTER COLUMN ID int NOT NULL
GO

ALTER TABLE <table name> ALTER COLUMN <column name> int identity (1,1) NOT NULL
GO
ALTER TABLE <table name> ALTER COLUMN <column name> int NOT NULL
GO

ALTER TABLE <table name> ADD ID int identity (1,1) NOT NULL
GO
ALTER TABLE <table name> ALTER COLUMN ID int NOT NULL
GO

use tempdb
if object_ID('#ttt','U') is not null drop table #ttt
go
create table #ttt(id int identity, val int)

alter table #ttt alter column id int not null

select name, is_identity from sys.columns
where object_id = OBJECT_ID('#ttt','U')

drop table #ttt

name	is_identity
id	1
val	0

alter table #ttt alter column id int identity not null

DECLARE @id int
SET @id = 0
Update YOUR_TABLE
Set @id = ID_FIELD=@id+1